WO2023008290A1

WO2023008290A1 - Spherical silica powder and method for producing spherical silica powder

Info

Publication number: WO2023008290A1
Application number: PCT/JP2022/028277
Authority: WO
Inventors: 博道加茂; 肇片山; 浩大福本
Original assignee: Ａｇｃ株式会社; Ａｇｃエスアイテック株式会社
Priority date: 2021-07-28
Filing date: 2022-07-20
Publication date: 2023-02-02
Also published as: KR20240037979A; JPWO2023008290A1; TW202319345A

Abstract

The present invention provides a new spherical silica powder having a sufficiently low loss tangent and exceptional miscibility with resin compositions. This spherical silica powder has a median diameter d50 of 0.5-20 μm, the product A×d50 of the specific surface area A (m2/g) and the median diameter d50 (μm) being 2.7-5.0 μm∙m2/g.

Description

Spherical silica powder and method for producing spherical silica powder

The present invention relates to spherical silica powder and a method for producing spherical silica powder.

In recent years, there has been a demand for smaller electronic devices, higher signal speeds, and higher wiring density. In order to meet this demand, adhesive films, insulating resin sheets such as prepreg, and resin compositions used for insulating layers formed on printed wiring boards must be made to have a low dielectric constant, a low dielectric loss tangent, and a low thermal expansion. is required.

The dielectric properties of ceramic materials are known, for example, from Non-Patent Document 1, etc., but all of them are properties of a sintered substrate. Silica (SiO ₂ ) has a small dielectric constant (3.9) and a small thermal expansion coefficient (3 to 7.9 ppm/° C.), and is promising as a filler material having a low dielectric constant and a low thermal expansion coefficient. Used in many applications. Therefore, it is expected to be widely used in high-frequency dielectric devices and the like.

In order to meet these demands, Patent Document 1 discusses reducing the dielectric loss tangent by heat-treating the fused spherical silica powder. Further, in Patent Document 2, crystalline silica is used as a raw material, and by molding it into a hollow shape, a low dielectric constant and a low dielectric loss tangent are studied.

Japanese Patent No. 6793282 Japanese Patent Application Laid-Open No. 2021-075438

A conventional spherical silica powder consists of base particles and minute adhering particles adhering thereto, and the specific surface area is particularly large due to the adhering particles. This limited the region where the dielectric loss tangent derived from surface residues could be reduced.
In the technique described in Patent Document 1, a spherical silica powder derived from silica stone is used to produce spherical silica powder. There is a problem that the surface area cannot be reduced and there is a limit to the reduction of the dielectric loss tangent. Moreover, in the technique described in Patent Document 2, it is necessary to granulate crystalline silica and melt it at a high temperature, so there is a problem in productivity.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a new spherical silica powder having a sufficiently small dielectric loss tangent and excellent miscibility with a resin composition.

As a result of intensive studies by the present inventors, it was found that the above problems can be solved by reducing the specific surface area according to the particle size to obtain a spherical silica powder in which the product of the specific surface area and the median diameter falls within a specific range. This led to the completion of the present invention.

The present invention relates to the following (1) to (10).
(1) The median diameter d50 is 0.5 to 20 μm, and the product A×d50 of the specific surface area A (m ² /g) and the median diameter d50 (μm) is 2.7 to 5.0 μm·m ² /g. spherical silica powder.
(2) The spherical silica powder according to (1), wherein the dielectric loss tangent of the spherical silica powder is 0.0020 or less at a frequency of 1 GHz.
(3) The spherical silica powder according to (1) or (2) above, wherein the kneaded product containing the spherical silica powder has a viscosity of 5000 mPa·s or less as measured by the following measuring method.
(Measuring method)
6 parts by mass of boiled linseed oil and 8 parts by mass of the spherical silica powder were mixed and ^kneaded at 2000 rpm for 3 minutes. Determine the viscosity at that point.
(4) Any one of (1) to (3) above, wherein the maximum IR peak intensity at 3300 to 3700 cm ⁻¹ derived from bound silanol groups on the surface of the spherical silica powder is 0.2 or less. Spherical silica powder as described.
(5) The spherical silica powder according to any one of (1) to (4) above, which contains 30 to 1500 ppm of Ti.
(6) A method for producing a spherical silica powder according to any one of (1) to (5) above, which comprises forming a spherical silica precursor by a wet process. .
(7) In accordance with JIS K0067:1992, when 1 g of the silica precursor is heat-dried at 850° C. for 0.5 hours, the weight loss of the silica precursor is 5.0 to 15.0% by mass. The method for producing a spherical silica powder according to (6) above.
(8) The method for producing spherical silica powder according to (6) or (7) above, wherein the silica precursor has a pore volume of 0.3 to 2.2 ml/g.
(9) A resin composition containing 5 to 90% by mass of the spherical silica powder according to any one of (1) to (5).
(10) A slurry composition containing 1 to 50% by mass of the spherical silica powder according to any one of (1) to (5).

According to the present invention, spherical silica powder having a small specific surface area and a sufficiently small dielectric loss tangent can be provided. Since the spherical silica powder of the present invention has a low dielectric loss tangent, it can exhibit an excellent low dielectric loss tangent even in a resin composition. In addition, since the specific surface area is sufficiently small relative to the particle size, it has excellent dispersibility in resins.

1 shows a scanning electron microscope image (SEM image) of the spherical silica powder obtained in Example 1. FIG.

The present invention will be described below, but the present invention is not limited by the exemplifications in the following description. In this specification, "-" indicating a numerical range means that the numerical values described before and after it are included as the lower limit and the upper limit.
In this specification, "mass" is synonymous with "weight".

The spherical silica powder of the present invention is solid silica, and has a median diameter d50 of 0.5 to 20 μm, which is the particle diameter at a cumulative volume of 50% in a volume-based particle size distribution curve, and a specific surface area A (m ² /g) and the median diameter d50 (μm) product A×d50 is 2.7 to 5.0 μm·m ² /g (2.7≦A×d50 (μm·m ² /g)≦5. 0).

When the median diameter d50 of the spherical silica powder is 0.5 μm or more, the dielectric loss tangent can be significantly reduced. In addition, if the median diameter becomes too large, the value of the grain gauge becomes large, so when the resin composition containing the spherical silica powder is formed into a sheet, for example, the minimum thickness of the sheet becomes large. . Therefore, in the present invention, the median diameter d50 of the spherical silica powder is set within the range of 0.5 to 20 μm. The median diameter d50 is preferably 0.5-10 μm, more preferably 1-5 μm.

The 10% particle size d10, which is the particle size at which the cumulative volume is 10% in the volume-based particle size distribution curve of the spherical silica powder, improves the uniform dispersibility in the resin composition, while improving the interaction between the spherical silica powder and the resin. 0.5 μm to 5.0 μm, more preferably 1.0 μm to 3.0 μm, from the viewpoint of increasing the

The ratio of the median diameter d50 to the 10% particle diameter d10 (d50/d10) is more than 1.0 and 5.0 from the viewpoint of enhancing the interaction between the spherical silica powder and the resin while improving the uniform dispersibility in the resin composition. The following are preferred, 1.3 to 4.0 are more preferred, and 1.5 to 3.0 are even more preferred.

The particle size distribution of the silica particles contained in the resin composition is preferably unimodal. The unimodal particle size distribution of the silica particles can be confirmed from the fact that the particle size distribution obtained by the laser diffraction/scattering method has one peak.

The maximum particle diameter (Dmax) of the spherical silica powder is preferably 150 times or less the median diameter d50, more preferably 100 times or less, still more preferably 50 times or less, and particularly preferably 10 times or less. When the maximum particle diameter (Dmax) is 150 times or less the median diameter d50, defects are less likely to occur when the sheet is processed. Also, the maximum particle diameter (Dmax) is preferably 1.2 times or more, more preferably 1.5 times or more, and even more preferably 2 times or more the median diameter d50.

The median diameter d50 is a volume-based cumulative 50% diameter determined by a laser diffraction particle size distribution analyzer (eg, “MT3300EXII” manufactured by Microtrack Bell Co., Ltd.). That is, the particle size distribution is measured by a laser diffraction/scattering method, the cumulative curve is obtained with the total volume of the spherical silica powder as 100%, and the particle diameter at the point where the cumulative volume is 50% on the cumulative curve.
The 10% particle diameter d10 is a volume-based cumulative 10% diameter determined by a laser diffraction particle size distribution analyzer (for example, “MT3300EXII” manufactured by Microtrac Bell Co., Ltd.). That is, the particle size distribution is measured by a laser diffraction/scattering method, a cumulative curve is obtained with the total volume of the spherical silica powder as 100%, and the particle size is the point on the cumulative curve where the cumulative volume is 10%.
The maximum particle diameter is also obtained by the same measurement as the median diameter d50 and the 10% particle diameter d10.

The specific surface area A of the spherical silica powder of the present invention is preferably in the range of 0.2-2.0 m ² /g. If the specific surface area is 0.2 m ² /g or more, when the spherical silica powder is contained in the resin composition, there is sufficient contact with the resin, so that compatibility with the resin is improved. When it is 0 m ² /g or less, the dielectric loss tangent can be reduced, so that an excellent low dielectric loss tangent can be exhibited even in the resin composition, and the dispersibility in the resin composition is improved. The specific surface area A is preferably 0.2 to 2.0 m ² /g, more preferably 0.5 to 2.0 m ² /g, still more preferably 0.5 to 1.5 m ² /g, and 0.8 to 1.5 m ² /g is particularly preferred. Here, the specific surface area A is preferably 2.0 m ² /g or less, more preferably 1.5 m ² /g or less, and preferably 0.2 m ² /g or more, preferably 0.5 m 2 /g or less. ² /g or more is more preferable, and 0.8 m ² /g or more is particularly preferable. In addition, it is substantially difficult to obtain one having a specific surface area A of less than 0.2 m ² /g.

The specific surface area is determined by the BET method based on the nitrogen adsorption method using a specific surface area/pore distribution measuring device (e.g., "BELSORP-miniII" manufactured by Microtrac Bell, "Tristar II" manufactured by Micromeritic, etc.). demand.

The product A×d50 of the specific surface area A (m ² /g) of the spherical silica powder and the median diameter d50 (μm) is 2.7 to 5.0 μm·m ² /g, preferably 2.7 to 4. 0.5 μm·m ² /g, more preferably 2.7 to 4.0 μm·m ² /g. A×d50 has a theoretical value of 2.7 [specific surface area = 6/(true density of silica 2.2 (g/cm ³ ) × median diameter d50 (μm))], and values below this are realistic. practically unattainable. The larger the value of A×d50, the larger the specific surface area per particle size and the larger the dielectric loss tangent. 0 μm·m ² /g or less.

The spherical silica powder preferably has a sphericity of 0.75 to 1.0. Since the specific surface area increases as the sphericity decreases, the dielectric loss tangent tends to increase, so the sphericity is preferably 0.75 or more. The sphericity is preferably 0.75 or more, more preferably 0.90 or more, even more preferably 0.93 or more, and the closer to 1.0 the better.

The sphericity is the maximum diameter (DL) and the short diameter (DS) perpendicular to each of arbitrary 100 particles in a photographic projection obtained by photographing with a scanning electron microscope (SEM). is measured, and the ratio of the minimum diameter (DS) to the maximum diameter (DL) (DS/DL) is calculated and can be expressed as an average value.

The spherical silica powder of the present invention preferably has a dielectric loss tangent of 0.0020 or less, more preferably 0.0010 or less, and even more preferably 0.0008 or less at a frequency of 1 GHz. In particular, in the measurement of dielectric loss tangent and dielectric constant of powder, a sample space becomes small at a frequency of 10 GHz or higher, resulting in poor measurement accuracy. When the dielectric loss tangent of the spherical silica powder at a frequency of 1 GHz is 0.0020 or less, an excellent effect of suppressing dielectric loss can be obtained, so that substrates and sheets with improved high frequency characteristics can be obtained. Since the transmission loss of the circuit is suppressed as the dielectric loss tangent becomes smaller, the lower limit value is not particularly limited.
From the same point of view, the dielectric constant of the spherical silica powder is preferably 5.0 or less, more preferably 4.5 or less, and even more preferably 4.1 or less at a frequency of 1 GHz.

The dielectric loss tangent and dielectric constant can be measured by the perturbation resonator method using a dedicated device (eg, "Vector Network Analyzer E5063A" manufactured by Keycom Co., Ltd.).

The spherical silica powder of the present invention preferably has a kneaded product containing the spherical silica powder with a viscosity of 5000 mPa·s or less as measured by the following measuring method.
(Measuring method)
6 parts by mass of boiled linseed oil specified in JIS K ⁵⁴²¹ :2000 and 8 parts by mass of spherical silica powder were mixed and kneaded at 2000 rpm for 3 minutes. for 30 seconds, and determine the viscosity at 30 seconds.

If the kneaded product has a viscosity of 5000 mPa s or less at a shear rate of 1 s ⁻¹ determined by the above measurement method, the amount of solvent added during molding and film formation of the resin composition containing spherical silica powder can be reduced, and the drying speed can be increased. You can do it faster and improve your productivity. In addition, when the specific surface area of the silica powder increases according to the particle size, the viscosity tends to increase when added to the resin composition. It can suppress the rise. The viscosity of the kneaded product is more preferably 4000 mPa·s or less, and even more preferably 3500 mPa·s or less.
The lower the viscosity of the kneaded product at a shear rate of 1 s ⁻¹ , the better the coating properties of the resin composition and the higher the productivity, so the lower limit is not particularly limited.

The IR peak intensity near 3746 cm ⁻¹ derived from isolated silanol groups on the surface of the spherical silica powder of the present invention is preferably 0.1 or less, more preferably 0.08 or less, and even more preferably 0.06 or less. . An isolated silanol group is a silanol (Si—OH) group that is not bound to water or the like adsorbed to silica particles. The amount of isolated silanol (Si—OH) groups on the silica particle surface is obtained by IR measurement. Specifically, after normalizing the IR spectrum at 800 cm ⁻¹ and adjusting the baseline at 3800 cm ⁻¹ , the relative value of the Si—OH peak intensity near 3746 cm ⁻¹ is obtained. If there are many isolated silanol groups on the particle surface, the dielectric loss tends to increase when the member mixed with the resin is used for electronic applications, but the IR peak intensity around 3746 cm ^-1 derived from the isolated silanol groups on the particle surface is 0.1 or less, the dielectric loss can be reduced.

In addition, the maximum IR peak intensity at 3300 to 3700 cm ⁻¹ derived from the bonded silanol groups on the surface of the spherical silica powder of the present invention is preferably 0.2 or less, more preferably 0.17 or less, and 0.5. 15 or less is more preferable. The bonded silanol group is a silanol (Si—OH) group bonded to water adsorbed to silica particles, silanol on the silica surface, or the like. The amount of bonded silanol (Si—OH) groups on the silica particle surface is obtained by IR measurement. Specifically, after normalizing the IR spectrum at 800 cm ⁻¹ and matching the baseline at 3800 cm ⁻¹ , the relative value of the bonded Si—OH peak intensity is determined from the maximum peak among those at 3300 to 3700 cm ⁻¹ . . If there are many bonded ^silanol groups on the particle surface, dielectric loss tends to increase when the member mixed with the resin is used for electronic applications. A dielectric loss can be reduced as the maximum IR peak intensity is 0.2 or less.

The spherical silica powder of the present invention is preferably non-porous particles. With porous particles, the oil absorption increases, the viscosity in the resin increases, the surface area increases, the amount of silanol (Si—OH) groups on the surface of the silica particles increases, and the dielectric loss tangent increases. tend to get worse. Specifically, the oil absorption is preferably 100 ml/100 g or less, more preferably 70 ml/100 g or less, and most preferably 50 ml/100 g or less. Although the lower limit is not particularly limited, it is practically difficult to reduce the oil absorption to 20 ml/100 g or less.
For measurement of oil absorption, it is preferable to use boiled linseed oil according to JIS K5101-13-2:2004.

The spherical silica powder of the present invention preferably contains titanium (Ti) in the range of 30 to 1500 ppm, more preferably 100 to 1000 ppm, even more preferably 100 to 500 ppm. The concentration of titanium can be measured by inductively coupled plasma (ICP) emission spectroscopy after adding perchloric acid and hydrofluoric acid to silica powder and heating the mixture to remove silicon as the main component.

　Ti is a component that is optionally included in the production of spherical silica powder. During the production of spherical silica powder, if fine powder is generated due to cracking of silica particles, the fine powder adheres to the surface of the base particles, increasing the specific surface area of the particles. By including Ti in the production of the spherical silica powder, it becomes easier to thermally compact during firing. This makes it difficult to crack during the post-treatment after calcination, so that the generation of fine powder can be suppressed, the amount of adhering particles adhering to the surface of the silica base particles can be reduced, and an increase in the specific surface area can be suppressed. By containing 30 ppm or more of Ti, it is easy to thermally compact during firing, so it is possible to suppress the generation of fine powder due to cracking. can suppress the deterioration of

The spherical silica powder of the present invention may contain impurity elements other than titanium (Ti) as long as the effects of the present invention are not impaired. Examples of impurity elements other than Ti include Na, K, Mg, Ca, Al, and Fe.
Among impurity elements, the total content of alkali metals and alkaline earth metals is preferably 2000 ppm or less, more preferably 1000 ppm or less, and even more preferably 200 ppm or less.

The spherical silica powder of the present invention may be treated with a silane coupling agent.
By treating the surface of the spherical silica powder with a silane coupling agent, the amount of residual silanol groups on the surface is reduced, the surface is made hydrophobic, moisture adsorption can be suppressed, dielectric loss can be improved, and the resin composition can be improved. In this case, the affinity with the resin is improved, and the dispersibility and the strength after resin film formation are improved.

Types of silane coupling agents include aminosilane coupling agents, epoxysilane coupling agents, mercaptosilane coupling agents, silane coupling agents, and organosilazane compounds. One type of silane coupling agent may be used, or two or more types may be used in combination.

The amount of the silane coupling agent attached is preferably 0.01 to 5 parts by mass, more preferably 0.02 to 5 parts by mass, and 0.1 to 2 parts by mass with respect to 100 parts by mass of the spherical silica powder. Part is more preferred. Here, the amount of the silane coupling agent attached is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, and 0.1 parts by mass or more with respect to 100 parts by mass of the spherical silica powder. is more preferable, 5 parts by mass or less is more preferable, and 2 parts by mass or less is even more preferable.

The fact that the surface of the spherical silica powder is treated with a silane coupling agent can be confirmed by detecting peaks due to the substituents of the silane coupling agent by IR. Moreover, the adhesion amount of the silane coupling agent can be measured by the amount of carbon.

(Method for producing spherical silica powder)
The method for producing spherical silica powder of the present invention includes forming a spherical silica precursor by a wet method. The wet method refers to a method including a step of using a liquid silica source and gelling it to obtain a raw material for spherical silica powder. Since spherical silica particles can be formed by using a wet method, there is no need to adjust the shape of the particles by pulverization or the like, and as a result, particles with a small specific surface area can be obtained. In addition, the wet method is less likely to produce particles significantly smaller than the average particle size, and the specific surface area tends to decrease after firing. In the wet method, the amount of impurity elements such as titanium can be adjusted by adjusting the impurities in the silica source, and the impurity elements can be uniformly dispersed in the particles.

Wet methods include, for example, a spraying method, an emulsion/gelation method, and the like. As the emulsion gelling method, for example, a dispersed phase and a continuous phase containing a silica precursor are emulsified, and the obtained emulsion is gelled to obtain a spherical silica precursor. As an emulsification method, a method of supplying a dispersed phase containing a silica precursor to a continuous phase through a micropore or a porous membrane to prepare an emulsion is preferred. This produces an emulsion with a uniform droplet size, resulting in spherical silica with a uniform particle size. As such an emulsification method, a micromixer method or a membrane emulsification method can be used. For example, the micromixer method is disclosed in WO2013/062105.

The pore volume of the spherical silica precursor obtained by the wet method is desirably 0.05 to 2.2 ml/g. When the pore volume of the silica precursor is 0.05 ml/g or more, the silica particles sufficiently shrink during firing, and the specific surface area can be reduced. Further, when the pore volume of the silica precursor is 2.2 ml/g or less, it is possible to prevent the bulk density of the pre-calcined material from becoming too large, thereby improving the productivity. The pore volume of the silica precursor is preferably 0.05-2.2 ml/g, more preferably 0.1-2.2 ml/g, more preferably 0.3-2.2 ml/g, 0.3-1.8 ml/g is more preferred, 0.6-1.8 ml/g is particularly preferred, and 0.7-1.5 ml/g is most preferred. Here, the pore volume of the silica precursor is preferably 0.05 ml/g or more, more preferably 0.1 ml/g or more, still more preferably 0.3 ml/g or more, and 0.6 ml/g or more. is particularly preferred, 0.7 ml/g or more is most preferred, 2.2 ml/g or less is preferred, 1.8 ml/g or less is more preferred, and 1.5 ml/g or less is most preferred.

The pore volume is determined by the BJH method based on the nitrogen adsorption method using a specific surface area/pore distribution measuring device (e.g., "BELSORP-miniII" manufactured by Microtrac Bell, "Tristar II" manufactured by Micromeritic, etc.). Calculated by

The ignition loss of the silica precursor obtained by the wet method is desirably 5.0 to 15.0% by mass, more preferably 6.0 to 13.0% by mass, and 7.0 to 12.0% by mass. % by mass is more preferred. The ignition loss is the sum of the mass of water adhering to the silica precursor and the mass of water generated by condensation of silanol groups contained in the silica precursor. Having a group promotes condensation during firing, making it easier to reduce silanol groups. If the ignition loss is too large, the yield at the time of firing decreases and the productivity deteriorates. Therefore, the ignition loss of the silica precursor is preferably 15.0% by mass or less, and 13.0% by mass or less. More preferably, 12.0% by mass or less is most preferable. If the ignition loss is too small, silanol groups tend to remain during firing, so the ignition loss of the silica precursor is preferably 5.0% by mass or more, more preferably 6.0% by mass or more, and 7.0% by mass. % or more is most preferable.

Here, the ignition loss is determined as the mass loss when 1 g of the silica precursor is dried by heating at 850°C for 0.5 hours in accordance with JIS K0067:1992.

The silica precursor preferably has an average pore diameter of 1.0 to 50.0 nm. When the average pore diameter is 1.0 nm or more, the inside of the particles can be uniformly made non-porous, and the dielectric loss tangent can be lowered without leaving air bubbles inside. When the average pore diameter is 50.0 nm or less, the silica particles can be densified (reduced specific surface area) without leaving pores by firing, so that the dielectric loss tangent can be lowered. The average pore diameter is preferably 1.0 to 50.0 nm, more preferably 2.0 to 40.0 nm, still more preferably 3.0 to 30.0 nm, particularly preferably 4.0 to 20.0 nm. . Here, the average pore diameter is preferably 1.0 nm or more, more preferably 2.0 nm or more, still more preferably 3.0 nm or more, particularly preferably 4.0 nm or more, and 50.0 nm or less. is preferably 40.0 nm or less, more preferably 30.0 nm or less, and particularly preferably 20.0 nm or less.

The average pore diameter is determined by the BET method based on the nitrogen adsorption method using a specific surface area/pore distribution measuring device (e.g., "BELSORP-miniII" manufactured by Microtrac Bell, "Tristar II" manufactured by Micromeritic, etc.). required by

The silica precursor preferably has a weight reduction rate of 10% or less when dried at 230° C. for 12 hours. When the weight reduction rate is 10% or less, when the silica precursor is fired while the particles are in contact with each other, the particles are less likely to be sintered, and spherical silica powder is more likely to be obtained.
The weight reduction rate is more preferably 9% or less, more preferably 8% or less, and particularly preferably 6% or less. The lower limit is not particularly limited.

When the water content of the obtained silica precursor is high and the weight reduction rate after drying at 230°C for 12 hours exceeds 10%, it is preferable to dry the silica precursor until it reaches 10% or less. Drying means include, for example, a spray dryer, stationary drying in a dryer, ventilation treatment with dry air, and the like.

The spherical silica powder is obtained by heat-treating the spherical silica precursor. In the heat treatment, the spherical silica powder is baked and densified, and the amount of silanol groups on the surface is reduced to lower the dielectric loss tangent. The heat treatment temperature is preferably 700 to 1600°C, more preferably 800 to 1500°C, even more preferably 900 to 1400°C. Here, the heat treatment temperature is preferably 700° C. or higher, more preferably 800° C. or higher, and most preferably 900° C. or higher. is preferably 1600° C. or lower, more preferably 1500° C. or lower, and most preferably 1400° C. or lower.

The heat treatment time may be appropriately adjusted according to the equipment to be used. For example, the heat treatment time is preferably 0.5 to 50 hours, more preferably 1 to 10 hours.

The atmosphere during the heat treatment may be an oxygen-containing atmosphere or an oxygen-free atmosphere. In the case of spheronization by a wet method, an organic substance such as an emulsifier is often used, and therefore the organic substance often remains in the silica precursor. When firing a silica precursor containing a small amount of organic matter, the organic matter is carbonized under conditions with little oxygen, which causes an increase in dielectric loss tangent and coloration. Therefore, when the silica precursor contains an organic substance, it is preferably fired in an oxygen-containing atmosphere, more preferably in an air atmosphere.

The method of the heat treatment is not particularly limited, but examples thereof include heat treatment by a stationary method, heat treatment by a rotary kiln method, heat treatment by spray combustion, and the like.
As for the heat treatment method, it is preferable that the spherical and porous silica precursor is fired while the particles are in contact with each other. When the silica precursor is fired while the particles are in contact with each other, it is possible to fire in a small volume. The unevenness is reduced, so that a spherical silica powder of uniform quality can be obtained. By firing the silica precursor in a state where the particles are in contact with each other, the firing conditions for each silica precursor are made uniform, and a constant quality can be maintained.

Since the particles of the spherical silica powder may be weakly sintered after firing, in such a case, crushing may be performed. Crushing is preferably carried out so that the average circularity of the particles does not fall below 0.90 in order to maintain the sphericity and surface area so as not to impair the effects of the present invention. Moreover, it is preferable that the surface area does not increase due to the crushing treatment. A large increase in the surface area due to the pulverization treatment means that some of the spherical particles are pulverized or fine particles are generated due to fine damage on the surface. An increase in surface area is not preferable because it leads to an increase in viscosity when dispersed in a resin and a deterioration in dielectric loss tangent.
Crushing can be performed using a crushing device such as a cyclone mill or a jet mill, and crushing can also be performed using a vibrating sieve.

The fired spherical silica powder may be surface-treated with a silane coupling agent. This step causes the silanol groups present on the surface of the spherical silica powder to react with the silane coupling agent, reduces the silanol groups on the surface, and improves the dielectric loss tangent. In addition, since the surface is made hydrophobic and the affinity for the resin is improved, the dispersibility in the resin is improved.

There are no particular restrictions on the surface treatment conditions, general surface treatment conditions may be used, and a wet treatment method or a dry treatment method can be used. A wet processing method is preferable from the viewpoint of uniform processing.

Silane coupling agents used for surface treatment include aminosilane coupling agents, epoxysilane coupling agents, mercaptosilane coupling agents, silane coupling agents, and organosilazane compounds. These may be used singly or in combination of two or more.

Specific examples of surface treatment agents include aminosilanes such as aminopropylmethoxysilane, aminopropyltriethoxysilane, ureidopropyltriethoxysilane, N-phenylaminopropyltrimethoxysilane, and N-2(aminoethyl)aminopropyltrimethoxysilane. system coupling agents, glycidoxypropyltrimethoxysilane, glycidoxypropyltriethoxysilane, glycidoxypropylmethyldiethoxysilane, glycidylbutyltrimethoxysilane, (3,4-epoxycyclohexyl)ethyltrimethoxysilane, etc. Epoxysilane coupling agents, mercaptosilane coupling agents such as mercaptopropyltrimethoxysilane, mercaptopropyltriethoxysilane, methyltrimethoxysilane, vinyltrimethoxysilane, octadecyltrimethoxysilane, phenyltrimethoxysilane, methacroxypropyl Silane _- based coupling agents such as trimethoxysilane, imidazolesilane, and triazinesilane, _CF3 ₍ _CF2 ) _7CH2CH2Si ₍ _OCH3 ) ₃ , _CF3 ₍ _CF2 ) _7CH2CH2SiCl3 _, CF ₃ ₍ CF2) _7CH2CH2Si ₍ _CH3 ) ₍ _OCH3 ) ₂ _, _CF3 ₍ CF2) _7CH2CH2Si ₍ _CH3 ) _C12 , _CF3 ₍ _CF2 ) _5CH2CH _2SiCl3 _, _CF3 ₍ _CF2 ₎ _5CH2CH2Si ₍ _OCH3 ₎ ₃ _, _{CF3CH2CH2SiCl3} _, _CF3CH2CH2Si ₍ _OCH3 ₎ ₃ _, _C8F17SO2 _N ₍ _C3H7 ₎ _CH2CH2CH2Si ₍ _OCH3 ₎ ₃ _, _{C7F15CONHCH2CH2CH2Si} ₍ _OCH3 ₎ ₃ _, _{C8F17CO2CH2CH2CH2Si} _{_} _{_} _{_} (OCH ₃ ) ₃ , C ₈ F ₁₇ —O—CF(CF ₃ )CF ₂ —O—C ₃ H ₆ SiCl ₃ , C ₃ F ₇ —O—(CF(CF ₃ )CF ₂ —O) ₂ — fluorine-containing silane coupling agents such as CF(CF ₃ )CONH—(CH ₂ ) ₃ Si(OCH ₃ ) ₃ , hexamethyldisilazane, hexaphenyldisilazane, organosilazane compounds such as trisilazane, cyclotrisilazane, 1,1,3,3,5,5-hexamethylcyclotrisilazane;

The treatment amount of the silane coupling agent is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, and further preferably 0.10 parts by mass or more with respect to 100 parts by mass of the spherical silica powder. It is preferably 5 parts by mass or less, more preferably 2 parts by mass or less.

Methods for treating with a silane coupling agent include, for example, a dry method in which a silane coupling agent is sprayed onto spherical silica powder, a wet method in which spherical silica powder is dispersed in a solvent, and then a silane coupling agent is added for reaction. are mentioned.

(Resin composition and slurry composition)
Since the spherical silica powder of the present invention has a small specific surface area, it has good dispersibility in various solvents and excellent miscibility with resin compositions.
The resin composition according to this embodiment contains the spherical silica powder of the present invention and a resin. The content of spherical silica powder in the resin composition is preferably 5 to 90% by mass, more preferably 10 to 85% by mass, still more preferably 10 to 80% by mass, particularly preferably 10 to 75% by mass, and 10% by mass. ~70% by weight is particularly preferred, and 15 to 70% by weight is most preferred. When the content of the spherical silica powder is 5% by mass or more, sufficient peel strength can be obtained, and when it is 90% by mass or less, the viscosity of the resin composition does not increase excessively, making it easy to handle. Here, the content of the spherical silica powder in the resin composition is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and 90% by mass or less. , more preferably 85% by mass or less, even more preferably 80% by mass or less, particularly preferably 75% by mass or less, and most preferably 70% by mass or less.

Resins include epoxy resins, silicone resins, phenol resins, melamine resins, urea resins, unsaturated polyester resins, fluorine resins, polyimide resins, polyamideimide resins, polyamide resins such as polyetherimide; Polyester resin; polyphenylene ether resin, polyphenylene sulfide resin, phenolic resin, orthodivinylbenzene resin, aromatic polyester resin, polysulfone, liquid crystal polymer, polyethersulfone, polycarbonate, maleimide modified resin, ABS (acrylonitrile-butadiene-styrene) resin, AAS (acrylonitrile-acrylic rubber/styrene) resin, AES (acrylonitrile/ethylene/propylene/diene rubber-styrene) resin, polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene One or more of hexafluoropropylene copolymer (FEP) and tetrafluoroethylene-ethylene copolymer (ETFE) can be used. Since the dielectric loss tangent in the resin composition also depends on the properties of the resin, the resin to be used should be selected in consideration of these properties.

The resin preferably contains a thermosetting resin. One type of thermosetting resin may be used, or two or more types may be used. Thermosetting resins include epoxy resins, polyphenylene ether resins, polyimide resins, phenol resins, orthodivinylbenzene resins, and the like. From the viewpoint of adhesion, heat resistance, etc., the thermosetting resin is preferably an epoxy resin, a polyphenylene ether resin, or an orthodivinylbenzene resin.

The weight average molecular weight of the thermosetting resin is preferably 1,000 to 7,000, more preferably 1,000 to 5,000, and still more preferably 1,000 to 3,000 from the viewpoint of adhesion, dielectric properties, and the like. A weight average molecular weight is calculated|required by polystyrene conversion using a gel permeation chromatography (GPC).

From the viewpoint of suppression of uneven distribution of silica particles, reduction of water absorption, low dielectric loss tangent, adhesion, etc., the content of spherical silica powder with respect to 100 parts by mass of thermosetting resin is preferably 10 to 400 parts by mass, and 50 to 300 parts by mass. parts is more preferred, and 70 to 250 parts by mass is even more preferred. In particular, when it is desirable to highly fill the silica particles, the content of the silica particles is preferably 80 parts by mass or more, more preferably 90 parts by mass or more.

Due to the action mechanism described above, the spherical silica powder is sufficiently wet and uniformly dispersed, and is highly likely to interact with the thermosetting resin. Therefore, even in the present composition in which the content is within this range, that is, in the present composition in which the thermosetting resin is filled with a large amount of spherical silica powder, both components are easily stabilized, and adhesion to the metal substrate layer is excellent. moldings can be formed.

In addition, the spherical silica powder of the present invention can be used as a filler for slurry compositions. The slurry composition refers to a muddy composition in which the spherical silica powder of the present invention is dispersed in an aqueous or oil medium.
The slurry composition preferably contains 1 to 50% by mass, more preferably 5 to 40% by mass, of spherical silica powder.

Oil-based media include acetone, methanol, ethanol, butanol, 2-propanol, 1-propanol, isobutyl alcohol, 1-butanol, 2-butanol, 2-methoxyethanol, 2-ethoxyethanol, 1-methoxy-2- propanol, 2-acetoxy-1-methoxypropane, propyl acetate, isobutyl acetate, butyl acetate, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, N,N-dimethylformamide, methyl isobutyl ketone, N-methylpyrrolidone, n-hexane, Examples include n-heptane, cyclohexane, methylcyclohexane, cyclohexanone and naphtha which is a mixture thereof. These may be used alone or as a mixture of two or more.

The resin composition and slurry composition may contain optional components in addition to the above resin and medium. Examples of optional components include dispersing aids, surfactants, fillers other than silica, and the like.

Dispersion equipment used for pigment dispersion can be used to disperse the mixed liquid containing the solvent and spherical silica powder. For example, mixers such as disper, homomixer, and planetary mixer, homogenizers (e.g., M Technic "Clairmix", PRIMIX "Filmix", Silverson "Abramix", etc.), paints Conditioner (manufactured by Red Devil), colloid mill (e.g. PUC "PUC Colloid Mill", IKA "Colloid Mill MK"), cone mills (e.g. IKA "Cone Mill MKO" etc.), ball mill, sand mill (For example, "Dyno Mill" manufactured by Shinmaru Enterprises Co., Ltd.), Attritor, Pearl Mill (eg, "DCP Mill" manufactured by Eirich Co., Ltd.), Media-type dispersers such as coball mills, wet jet mills (For example, Genus Co., Ltd. " Genus PY", Sugino Machine "Starburst", Nanomizer "Nanomizer", etc.), M Technic "Crea SS-5", Nara Machinery "MICROS", etc. Medialess dispersers, other roll mills , a kneader, and the like. Among them, those that do not use grinding media (balls, beads, etc.) are desirable. This is because the use of pulverizing media raises concerns about contamination of worn media. Specifically, wet jet mills ("Genus PY" manufactured by Genus, "Starburst" manufactured by Sugino Machine, "Nanomizer" manufactured by Nanomizer, etc.), "Crea SS-5" manufactured by M Technic, and Nara Machinery. A medialess dispersing machine such as "MICROS" manufactured by Fujikura is desirable.

Also, the temperature during the dispersion treatment is preferably 0 to 100°C. By carrying out the dispersion treatment within the above temperature range, the viscosity of the solvent can be appropriately maintained, the productivity can be maintained, and the evaporation of the solvent can be suppressed to easily control the solid content. The treatment temperature is preferably 0 to 100°C, more preferably 5 to 90°C, even more preferably 10 to 80°C. Here, the treatment temperature is more preferably 5° C. or higher, more preferably 10° C. or higher, and more preferably 90° C. or lower, further preferably 80° C. or lower.

The time for the dispersion treatment may be appropriately set according to the dispersing device to be used so that the particle destruction does not proceed, but it is preferably 0.5 to 60 minutes, more preferably 0.5 to 10 minutes, and 0.5 to 10 minutes. 0.5 to 5 minutes is more preferred.

After that, the aggregates of the spherical silica powder that remained undispersed even in the dispersion treatment are wet-classified. Examples of wet classification include classification using a sieve and centrifugal force. When using a sieve, it is preferable to classify with a sieve having an opening of 100 μm or less. As the sieve, for example, it is preferable to use a metal having a dense lattice structure such as an electroformed sieve.

The mesh size of the sieve is preferably 0.2-100 μm, more preferably 0.5-75 μm, even more preferably 0.5-50 μm, and particularly preferably 1-35 μm. Here, the sieve opening is preferably 100 μm or less, more preferably 75 μm or less, even more preferably 50 μm or less, particularly preferably 35 μm or less, and preferably 0.2 μm or more, and 0.5 μm or more. is more preferable, and 1 μm or more is even more preferable.

After that, it may be diluted or concentrated as necessary to adjust to an appropriate concentration. Concentration methods include vaporization concentration, solid-liquid separation, and the like.

In addition, in the method for producing the slurry composition of the present invention, a silane coupling agent may be added to the mixed liquid of the solvent and the spherical silica powder. Examples of the silane coupling agent include the silane coupling agents described above.

When a resin film is produced using the resin composition containing the spherical silica powder of the present invention, the dielectric loss tangent thereof at a frequency of 10 GHz is preferably 0.012 or less, more preferably 0.010 or less, and 0.009. More preferred are: When the resin film has a dielectric loss tangent of 0.012 or less at a frequency of 10 GHz, the resin film has excellent electrical properties and can be expected to be used in electronic devices, communication devices, and the like. Since the transmission loss of the circuit is suppressed as the dielectric loss tangent becomes smaller, the lower limit value is not particularly limited.

In addition, when a resin film is produced using the resin composition containing the spherical silica powder of the present invention, the dielectric constant thereof at a frequency of 10 GHz is preferably 2.0 to 3.5, and the lower limit is 2.0. The upper limit is more preferably 2 or more, more preferably 2.3 or more, and the upper limit is more preferably 3.2 or less, further preferably 3.0 or less. When the relative permittivity of the resin film at a frequency of 10 GHz is within the above range, it is expected to be used in electronic devices, communication devices, etc., because it has excellent electrical properties.

The dielectric constant can be measured by a perturbation-type resonator method using a dedicated device (for example, "Vector Network Analyzer E5063A" manufactured by Keycom Co., Ltd.).
The dielectric loss tangent of the resin film can be measured using a split-post dielectric resonator (SPDR) (manufactured by Agilent Technologies, for example).

Also, the resin film preferably has an average coefficient of linear expansion of 10 to 50 ppm/°C. When the average coefficient of linear expansion is within the above range, the range is close to the coefficient of thermal expansion of copper foil, which is widely used as a base material, and thus the electrical properties are excellent. The average coefficient of linear expansion is more preferably 12 ppm/°C or higher, more preferably 15 ppm/°C or higher, and more preferably 40 ppm/°C or lower, further preferably 30 ppm/°C or lower.

The average coefficient of linear expansion is determined by using a thermomechanical analyzer (for example, "TMA-60" manufactured by Shimadzu Corporation), heating the resin film at a load of 5 N and a temperature increase rate of 2 ° C./min, and increasing from 30 ° C. It is obtained by measuring the dimensional change of the sample up to 150° C. and calculating the average.

In addition, the spherical silica powder of the present invention can be used as various fillers, and is particularly used in the production of electronic substrates used in electronic devices such as personal computers, notebook computers and digital cameras, and communication devices such as smartphones and game machines. It can be suitably used as a filler for resin compositions. Specifically, the silica powder of the present invention is used in resin compositions, prepregs, metal foil-clad laminates, printed wiring boards, and resins for low dielectric loss tangent, low transmission loss, low moisture absorption, and improved peel strength. It is also expected to be applied to sheets, adhesive layers, adhesive films, solder resists, bump reflow, rewiring insulating layers, die bonding materials, sealing materials, underfills, mold underfills, laminated inductors, and the like.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these. In the following description, the same common components are used. Moreover, unless otherwise specified, "parts" and "%" represent "mass parts" and "mass%". Examples 1-12 are working examples, and examples 13-14 are comparative examples.

<Test Example 1>
(Example 1)
As a spherical silica precursor, silica powder 1 produced by a wet method (manufactured by AGC Si Tech: H-31, d50=3.5 μm) was used. When the titanium (Ti) content of silica powder 1 was measured, it was 300 ppm. 15 g of silica powder 1 was filled in an alumina crucible and heat-treated at an electric furnace temperature of 1300° C. for 1 hour. After the heat treatment, the mixture was cooled to room temperature and ground in an agate mortar to obtain a spherical silica powder.

(Example 2)
Spherical silica powder was obtained in the same manner as in Example 1, except that silica powder 2 (manufactured by AGC Si Tech Co., Ltd.: H-51, d50 = 5.5 µm) produced by a wet method was used as the spherical silica precursor. got
The Ti content of the silica powder 2 used as the spherical silica precursor was measured and found to be 300 ppm.

(Example 3)
Spherical silica powder was obtained in the same manner as in Example 1, except that silica powder 3 (manufactured by AGC Si Tech Co., Ltd.: H-121, d50 = 13 μm) produced by a wet method was used as the spherical silica precursor. rice field.
In addition, when the Ti content of silica powder 3 used as a spherical silica precursor was measured, it was 300 ppm.

(Example 4)
Spherical silica powder was obtained in the same manner as in Example 1, except that silica powder 4 (manufactured by AGC Si Tech Co., Ltd.: H-201, d50 = 20 µm) produced by a wet method was used as the spherical silica precursor. rice field.
The Ti content of the silica powder 4 used as the spherical silica precursor was measured and found to be 300 ppm.

(Example 5)
15 g of silica powder 1 produced by a wet method (manufactured by AGC Si Tech Co., Ltd.: H-31, d50 = 3.5 μm, Ti content = 300 ppm) similar to that used in Example 1 was filled in a SUS vat. and a constant temperature and humidity chamber for 24 hours at a temperature of 40° C. and a relative humidity (RH) of 80% to obtain a spherical silica precursor.
The entire amount of the spherical silica precursor obtained was filled in an alumina crucible and heat-treated at an electric furnace temperature of 1300° C. for 1 hour. After the heat treatment, the mixture was cooled to room temperature and ground in an agate mortar to obtain a spherical silica powder.

(Example 6)
15 g of silica powder 1 (manufactured by AGC Si Tech Co., Ltd.: H-31, d50 = 3.5 μm, Ti content = 300 ppm) produced by a wet method similar to that used in Example 1 was placed in a 200 ml beaker, After adding 100 ml of ethanol and stirring for 1 hour, solid-liquid separation was performed, and the obtained solid was vacuum-dried at 60° C. for 24 hours to obtain a spherical silica precursor.
The entire amount of the spherical silica precursor obtained was filled in an alumina crucible and heat-treated at an electric furnace temperature of 1300° C. for 1 hour. After the heat treatment, the mixture was cooled to room temperature and ground in an agate mortar to obtain a spherical silica powder.

(Example 7)
15 g of silica powder 1 (manufactured by AGC Si Tech Co., Ltd.: H-31, d50 = 3.5 μm, Ti content = 300 ppm) produced by a wet method similar to that used in Example 1 was placed in a 200 ml beaker, Add 100 ml of distilled water, heat to 80°C over 1 hour in a water bath, stir for 4 hours while keeping the water temperature in a beaker at 78 to 82°C, separate solid and liquid, and cool the obtained solid to 100°C. for 24 hours to obtain a spherical silica precursor.
The entire amount of the spherical silica precursor obtained was filled in an alumina crucible and heat-treated at an electric furnace temperature of 1300° C. for 1 hour. After the heat treatment, the mixture was cooled to room temperature and ground in an agate mortar to obtain a spherical silica powder.

(Example 8)
Spherical silica powder was obtained in the same manner as in Example 1, except that silica powder 5 (manufactured by AGC Si Tech Co., Ltd.: H-33, d50 = 3.0 μm) was used as the spherical silica precursor. got
In addition, when the Ti content of the silica powder 5 used as the spherical silica precursor was measured, it was 300 ppm.

(Example 9)
Spherical silica powder was obtained in the same manner as in Example 1 except that silica powder 6 produced by a wet method (manufactured by AGC Si Tech Co., Ltd.: H-51, d50 = 5.5 µm) was used as the spherical silica precursor. got
The Ti content of the silica powder 6 used as the spherical silica precursor was measured and found to be 1450 ppm.

(Example 10)
Spherical silica powder was obtained in the same manner as in Example 1 except that silica powder 7 produced by a wet method (manufactured by AGC Si Tech Co., Ltd.: H-51, d50 = 5.5 µm) was used as the spherical silica precursor. got
The Ti content of the silica powder 7 used as the spherical silica precursor was measured and found to be 35 ppm.

(Example 11)
10 g of the silica powder obtained in Example 1, 10 mg of 3-(methacryloyloxy)propyltrimethoxysilane, and 5 g of decane were mixed, and the solvent was distilled off by vacuum drying at 150° C. to obtain the surface-treated spherical silica powder. Obtained.

(Example 12)
As a spherical silica precursor, silica powder 1 produced by a wet method (manufactured by AGC Si Tech: H-31, d50=3.5 μm) was used. When the titanium (Ti) content of silica powder 1 was measured, it was 300 ppm. 15 g of silica powder 1 was filled in an alumina crucible and heat-treated at an electric furnace temperature of 1050° C. for 6 hours. After the heat treatment, the mixture was cooled to room temperature and ground in an agate mortar to obtain a spherical silica powder.

(Example 13)
Spherical silica powder 8 (manufactured by Denka: FB-5D) produced from raw material silica produced by a dry method was used. When the Ti content of the spherical silica powder 8 was measured, it was 22 ppm. 15 g of spherical silica powder 8 was filled in an alumina crucible and heat-treated at an electric furnace temperature of 1300° C. for 1 hour. After the heat treatment, the mixture was cooled to room temperature and ground in an agate mortar to obtain a spherical silica powder.

(Example 14)
Spherical silica powder 9 (manufactured by Admatechs: SC-04) produced from raw material silica produced by the VMC method was used as it was. When the Ti content of the spherical silica powder 9 was measured, it was 28 ppm.

The spherical silica powders of Examples 1 to 14 were evaluated as follows. Table 1 shows the results.
Further, a scanning electron microscope observation image (SEM image) of the spherical silica powder of Example 1 is shown in FIG.

"evaluation"
1. Median Diameter The median diameter was measured using a laser diffraction particle size distribution analyzer (Microtrac Bell MT3300EXII). Measurement was performed after the spherical silica powder was dispersed by irradiating ultrasonic waves three times for 60 seconds in the apparatus. The measurement was performed twice for 60 seconds each, and the average value was obtained.

2. Specific Surface Area Spherical silica powder was dried under reduced pressure at 230° C. to completely remove moisture, and used as a sample. The specific surface area of this sample was determined by the multi-point BET method using nitrogen gas using an automatic specific surface area/pore size distribution measuring device "Tristar II" manufactured by Micromeritic.

3. Pore Volume Silica powder used as a precursor was dried under reduced pressure at 230° C. to completely remove moisture, and used as a sample. The pore volume of this sample was determined by the BJH method using nitrogen gas using an automatic specific surface area/pore size distribution analyzer "Tristar II" manufactured by Micromeritic.

4. Loss on ignition In accordance with JIS K0067:1992, 1 g of silica powder used as a precursor was dried by heating at 850°C for 0.5 hours, and the weight loss on ignition was defined as the loss on ignition.

5. Ti concentration After adding perchloric acid and hydrofluoric acid to the silica powder used as a precursor and heating to remove silicon as the main component, the Ti concentration was measured by inductively coupled plasma (ICP) emission spectrometry.

6. Dielectric loss tangent Dielectric loss tangent is measured three times at a test frequency of 1 GHz, a test temperature of about 24°C, a humidity of about 45%, and a perturbation resonator method using a dedicated device (vector network analyzer E5063A, manufactured by Keycom). Measurements were made. Specifically, after vacuum-drying the spherical silica powder at 150°C, the powder was filled into a polytetrafluoroethylene (PTFE) cylinder while fully tapping, and the dielectric constant was measured together with the container. The dielectric loss tangent was converted using the body filling factor.

7. Amount of Silanol Groups The amount of silanol groups on the particle surface was measured by infrared spectroscopy.
The infrared spectroscopic spectrum was measured by diffuse reflection method using IR Prestige-21 (manufactured by Shimadzu Corporation) by dispersing spherical silica powder in diamond. The measurement range was 400 to 4000 cm ^-1 , the resolution was 4 cm ^-1 , and the number of integrations was 128 times.
Dilution to diamond powder is defined as [mass dilution rate] = ([sample mass]) / ([diamond mass] + [sample mass]), [mass dilution rate] = 85-2.5 x [BET ratio surface area].
Also, the spherical silica powder used was vacuum-dried at 180° C. for 1 hour.
After normalizing the IR spectrum at 800 cm ⁻¹ and adjusting the baseline at 3800 cm ⁻¹ , from the relative value of the Si—OH peak intensity near 3746 cm ⁻¹ and the maximum peak among those at 3300 to 3700 cm ⁻¹ , the binding A relative value of the Si—OH peak intensity was obtained.

8. Viscosity and Particle Gauge In order to examine the resin dispersibility of the spherical silica powder, the following test was carried out.
6 parts of boiled linseed oil (manufactured by Sankei Sangyo Co., Ltd.) and 8 parts of spherical silica powder are mixed, and kneaded at 2000 rpm for 3 minutes with an Awatori Mixer (manufactured by Thinky Corporation), which is a rotation-revolution type agitator, to obtain a kneaded product. made. The resulting kneaded product was measured at a shear rate of 1 s ⁻¹ for 30 seconds using a rotary rheometer to obtain the viscosity at 30 seconds. The viscosity measured only with boiled linseed oil was 46 mPa·s.
Moreover, the obtained kneaded material was measured by the JIS K5400:1990 grain gauge method.

9. Moisture Absorption In order to examine the hygroscopicity of the spherical silica powder, the following test was carried out.
After drying the spherical silica particles at 200° C., 5 g was weighed in an aluminum dish with a diameter of 10 cm and spread evenly. It was measured by the Karl Fischer method (coulometric titration method) after being left in an environment of 90% RH at 40° C. for 24 hours.
[Conditions for the Karl Fischer method (coulometric titration method)]
Trace moisture measuring device (CA-200 type, manufactured by Mitsubishi Chemical Analytic Tech)
Moisture vaporizer (VA-200, manufactured by Mitsubishi Chemical Analytic Tech)
Anolyte (Hydranal Coulomat AG-OVEN, manufactured by Hayashi Pure Chemical Co., Ltd.)
Catholyte (Hydranal Coulomat CG, manufactured by Hayashi Pure Chemical Co., Ltd.)
Heating temperature: 200°C
Nitrogen flow rate: about 250 ml/min

From the results in Table 1, as a result of changing the product of the specific surface area and the median diameter of the spherical silica powder, the spherical silica powders of Examples 1 to 12 have low dielectric loss tangents, viscosities, grain gauges, and moisture absorption amounts. 13 and 14, it was found that the dielectric loss tangent deteriorates when the product of the specific surface area and the median diameter becomes too large. The fact that the specific surface area is large relative to the median diameter suggests the presence of fine particles and surface roughness, which is thought to increase the abundance of surface residues and increase the dielectric loss tangent. . In addition, it is believed that the presence of fine particles and surface roughness increases the viscosity of the resin composition, resulting in an increase in viscosity. Also, the median diameter is preferably 0.5 to 20 μm. This is because if the median diameter is small, the viscosity increases, and if the median diameter is large, the grain gauge increases.

Moreover, from Examples 1 to 14, it was found that the dielectric loss tangent decreased when the ignition loss of the silica precursor was large. This is probably because if the ignition loss of the silica precursor is less than 1.0%, silanol groups tend to remain during firing, which increases the dielectric loss tangent. If the ignition loss of the silica precursor exceeds 15.0%, it is predicted that the loss during firing will increase and the yield will deteriorate.
From Examples 1 to 14, it was found that the pore volume of the silica precursor is also related to the dielectric loss tangent. If the pore volume is too small, the silica will not shrink when the silica precursor is fired, and the specific surface area will not easily decrease, so it is assumed that the dielectric loss tangent will increase.

<Test Example 2>
Using the spherical silica powders of Examples 1, 3, 11 and 14, resin films were produced.
25 parts of a biphenyl-type epoxy resin (epoxy equivalent: 276, “NC-3000” manufactured by Nippon Kayaku Co., Ltd.) was heated and dissolved in 13 parts of methyl ethyl ketone (MEK) while stirring. After cooling to room temperature, 32 parts of an active ester curing agent ("HP8000-65T" manufactured by DIC Corporation, a toluene solution with an active group equivalent weight of 223 and a non-volatile component of 65%) was mixed and mixed with a rotation-revolution stirrer. The mixture was kneaded at 2000 rpm for 5 minutes with a Thinky Mixer. Subsequently, 0.3 parts of 4-dimethylaminopyridine (DMAP) and 1.8 parts of 2-ethyl-4-methylimidazole (manufactured by Shikoku Kasei Kogyo Co., Ltd. "2E4MZ") were mixed as a curing accelerator and kneaded. The mixture was kneaded with Taro at 2000 rpm for 5 minutes. 65.2 parts of spherical silica powder was mixed therein, and the mixture was mixed at 2000 rpm for 5 minutes with a Mixer.

Next, a release-treated transparent polyethylene terephthalate (PET) film ("PET5011 550" manufactured by Lintec, thickness 50 μm) was prepared. Using an applicator, the resulting varnish was applied to the release-treated surface of the PET film so that the thickness after drying was 40 μm, dried in a gear oven at 190° C. for 90 minutes, and cured. Then, it was cut to prepare a cured resin film (evaluation sample) of 200 mm long×200 mm wide×40 μm thick.

(1) Evaluation of dielectric loss tangent The obtained evaluation sample was measured for dielectric loss tangent (measurement frequency: 10 GHz) with a split-post dielectric resonator (manufactured by Agilent Technologies). Further, the obtained evaluation sample was stored in a constant temperature and humidity chamber at 85° C. and 85% RH for 24 hours, and the dielectric loss tangent was similarly measured for the evaluation sample after moisture absorption.

(2) Measurement of Average Coefficient of Linear Expansion An evaluation sample was cut into a size of 3 mm×25 mm. This sample was heated using a thermomechanical analyzer ("TMA-60" manufactured by Shimadzu Corporation) under a load of 5N and a temperature increase rate of 2°C/min. Then, the dimensional change of the sample was measured from 30° C. to 150° C., and the average coefficient of linear expansion (ppm/° C.) was obtained by dividing the dimensional change of the long side by the temperature.

The results are shown in Table 2.

From the results in Table 2, the dielectric loss tangent of the spherical silica powders of Examples 1, 3 and 11 was small, so the dielectric loss tangent of the resin composition was significantly improved. In addition, since the spherical silica powder of the present invention does not easily absorb moisture, the resin composition is less hygroscopic and exhibits good electrical properties even after storage under humidified conditions.

Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on a Japanese patent application (Japanese patent application 2021-123495) filed on July 28, 2021 and a Japanese patent application (Japanese patent application 2021-194372) filed on November 30, 2021, and the content is Incorporated here as a reference.

Claims

Spherical having a median diameter d50 of 0.5 to 20 μm and a product A×d50 of the specific surface area A (m 2 /g) and the median diameter d50 (μm) of 2.7 to 5.0 μm·m 2 /g silica powder.
The spherical silica powder according to claim 1, wherein the dielectric loss tangent of the spherical silica powder is 0.0020 or less at a frequency of 1 GHz.
3. The spherical silica powder according to claim 1, wherein the kneaded material containing said spherical silica powder has a viscosity of 5000 mPa.s or less as measured by the following measuring method.
(Measuring method)
6 parts by mass of boiled linseed oil and 8 parts by mass of the spherical silica powder were mixed and kneaded at 2000 rpm for 3 minutes. Determine the viscosity at that point.
The spherical silica powder according to any one of claims 1 to 3, wherein the maximum IR peak intensity at 3300 to 3700 cm -1 originating from the bonded silanol groups on the surface of the spherical silica powder is 0.2 or less.
The spherical silica powder according to any one of claims 1 to 4, wherein the spherical silica powder contains 30 to 1500 ppm of Ti.
A method for producing the spherical silica powder according to any one of claims 1 to 5, comprising forming a spherical silica precursor by a wet method.
In accordance with JIS K0067: 1992, when 1 g of the silica precursor is heat-dried at 850 ° C. for 0.5 hours, the weight loss of the silica precursor is 5.0 to 15.0% by mass. The method for producing the spherical silica powder according to claim 6.
The method for producing spherical silica powder according to claim 6 or 7, wherein the silica precursor has a pore volume of 0.3 to 2.2 ml/g.
A resin composition containing 5 to 90% by mass of the spherical silica powder according to any one of claims 1 to 5.
A slurry composition containing 1 to 50% by mass of the spherical silica powder according to any one of claims 1 to 5.